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Old 12th May 2011, 18:08   #16
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Default Re: Tata Marco Polo vs Ashok Leyland Rear Engine on DTC Fleet

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Originally Posted by Mpower View Post
Speed retarder limits top speed right. How does it affect acceleration?
Because the retarder acts in every gear and the transmission being automatic, upshifting doesn't help much! So DTC drivers often take recourse to switching off the AC, much to the chagrin of passengers who had paid more for travelling in AC comfort!
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Old 12th May 2011, 18:09   #17
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Default Re: Tata Marco Polo vs Ashok Leyland Rear Engine on DTC Fleet

@directinjection

As for the 8.3L engines, that I think was more of a stop gap arrangement from TML to meet orders in time. The 5.9L engines are made at the Tata Cummins Factory in Jamshedpur itself. This factory produces only these 5.9L engines and supplies also a large number of engines to the factory at Jamshedpur. So to meet the orders for the Commonwealth Games, as an intermediate arrangement some buses were provided with the 8.3L CNG engine from Cummins procured from Cummins India Limited, from their factory in Pune. This engine is no longer available, as the need to supply is no longer that urgent. As of now AC/Non-AC versions are only available with the 230hp 5.9L engine only.

Also, I dont see what exactly you mean by a retarder. The only thing that comes to mind is to limit the accelerating capability of the bus using the ECU.

The lack of acceleration of these buses compared to old bluelines can be explained by the gearing. The automatic gearbox would want to improve fuel efficiency rather than speed and acceleration. Thus it would want to shift to higher gears as soon as possible.
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Old 12th May 2011, 18:22   #18
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Default Re: Tata Marco Polo vs Ashok Leyland Rear Engine on DTC Fleet

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@directinjection

As for the 8.3L engines, that I think was more of a stop gap arrangement from TML to meet orders in time. The 5.9L engines are made at the Tata Cummins Factory in Jamshedpur itself. This factory produces only these 5.9L engines and supplies also a large number of engines to the factory at Jamshedpur. So to meet the orders for the Commonwealth Games, as an intermediate arrangement some buses were provided with the 8.3L CNG engine from Cummins procured from Cummins India Limited, from their factory in Pune. This engine is no longer available, as the need to supply is no longer that urgent. As of now AC/Non-AC versions are only available with the 230hp 5.9L engine only.

Also, I dont see what exactly you mean by a retarder. The only thing that comes to mind is to limit the accelerating capability of the bus using the ECU.

The lack of acceleration of these buses compared to old bluelines can be explained by the gearing. The automatic gearbox would want to improve fuel efficiency rather than speed and acceleration. Thus it would want to shift to higher gears as soon as possible.
It is not that TML is under any obligation to buy engines only from Tata Cummins Ltd. (TCL) which in any case produces only the B series engine in 5.9 litre (6 pot) and 3.8 litre (4-pot) versions. Can Tata limit its engine options to only one engine, what with the growing trend towards higher power even in India? As of now, there is no plan to make other Cummins engine models at TCL and so TML procures other models of Cummins engines like "C" and "L" series directly from Cummins India Ltd.

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Also, I dont see what exactly you mean by a retarder. The only thing that comes to mind is to limit the accelerating capability of the bus using the ECU.
The tender itself specified that all buses must be fitted with speed retarders, in order to ensure safety.

8.3 wasn't a stop-gap arrangement.
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Old 12th May 2011, 18:40   #19
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Default Re: Tata Marco Polo vs Ashok Leyland Rear Engine on DTC Fleet

Tata primarily buys engines from TCL only, which happens to be a subsidiary which officially commits 50% of its production for Tata Motors, though practically its more than 90%. There are no plans to make any other engines because TML does not require any other engine. They use only the 5.9L Bseries engines. The day Tata will want different engines TCL will make necessary changes for making them.

If Tata could get engines from TCL why would it go to CIL at all, which will have to ship engines from Pune and will probably cost higher as well. Remember sourcing parts from a subsidiary is different from a completely different company. True CIL does provide a few engines, but they are very limited in number. As of now only the Tata Prima engines are sourced from them. That too because the low volumes of the Prima dont merit a makeover of the TCL plant to make those engines. And also why would they change their mind and go back to the 5.9L engines for the AC versions now??

I know speed retarders exist, but I would imagine they would limit top speed by limiting the engine rpms. They should not effect acceleration at all, unless they want to, by changing the amount of fuel that is injected.
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Old 12th May 2011, 20:07   #20
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Default Re: Tata Marco Polo vs Ashok Leyland Rear Engine on DTC Fleet

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Originally Posted by julupani View Post
Tata primarily buys engines from TCL only, which happens to be a subsidiary which officially commits 50% of its production for Tata Motors, though practically its more than 90%. There are no plans to make any other engines because TML does not require any other engine. They use only the 5.9L Bseries engines. The day Tata will want different engines TCL will make necessary changes for making them.

If Tata could get engines from TCL why would it go to CIL at all, which will have to ship engines from Pune and will probably cost higher as well. Remember sourcing parts from a subsidiary is different from a completely different company. True CIL does provide a few engines, but they are very limited in number. As of now only the Tata Prima engines are sourced from them. That too because the low volumes of the Prima dont merit a makeover of the TCL plant to make those engines. And also why would they change their mind and go back to the 5.9L engines for the AC versions now??

I know speed retarders exist, but I would imagine they would limit top speed by limiting the engine rpms. They should not effect acceleration at all, unless they want to, by changing the amount of fuel that is injected.
So exactly what are you trying to say? You contradict yourself. First you say TML does not require any other engine but also admit they use other engines in Prima. Secondly, on the one hand you say that the original plan did not require supplying AC buses with 8.3L engine and that it has now been stopped but then you also question why TML would change its mind now and go back to 5.9L engines for AC buses. Did I ever say TML is going back to 5.9L for AC buses? That's something you alleged, not me.

But cheers anyway!
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Old 12th May 2011, 21:04   #21
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Default Re: Tata Marco Polo vs Ashok Leyland Rear Engine on DTC Fleet

I said Tata does not require any other engine from TCL, and not any other engine at all. Tata uses about 300-400 engines from TCL every day. I doesnt require that many engines for the Prima from CIL every month. So the requirement from CIL is negligible. I did also mention that once requirement of Prima engines is high enough I am sure TCL will retool itself to making the engines that Tata requires.

As for the return to 5.9L CNG engines for AC buses, I am not alleging. I know. My mistake was in assuming that you knew too. You can check out Tata's buses new site if you want confirmation. I formed that as a question for you to answer why Tata changed its mind and moved back to a lower powered bus in the AC versions.

Sorry for the confusion.
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Old 14th May 2011, 11:30   #22
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Default Re: Tata Marco Polo vs Ashok Leyland Rear Engine on DTC Fleet

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... As of now only the Tata Prima engines are sourced from them. That too because the low volumes of the Prima dont merit a makeover of the TCL plant to make those engines....
How about the BS III Divo engines. Think they are from CIL?
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Old 14th May 2011, 12:17   #23
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Default Re: Tata Marco Polo vs Ashok Leyland Rear Engine on DTC Fleet

I am not exactly sure whether those engines are made by CIL or TCL. Those are the latest generation 6.7L Bseries engines, which I think Tata will make a full move to once BSIV norms are to be met in a few years time. These newer ISBe are also in use on the Prima tippers. And I had heard production would start at TCL itself in view of the move to these new-gen engines. But like I said I am not sure.
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Old 3rd December 2011, 12:52   #24
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Default Re: Tata Marco Polo vs Ashok Leyland Rear Engine on DTC Fleet

It is shocking to see the praises on Tata Marcopolo. In Bangalore, Marcopolo buses will not be used anymore as it is too under-powered.

BMTC will continue with Volvo and has introduced Corona in the place of Marcopolo which is BS4.
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Old 3rd December 2011, 23:26   #25
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Default Re: Tata Marco Polo vs Ashok Leyland Rear Engine on DTC Fleet

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It is shocking to see the praises on Tata Marcopolo. In Bangalore, Marcopolo buses will not be used anymore as it is too under-powered.

BMTC will continue with Volvo and has introduced Corona in the place of Marcopolo which is BS4.
Wrong. BMTC has placed orders for an equal number of fully built Marcopolos, built on LPO1618 chassis, and LPO1618 chassis.

Corona Skypak bus uses the same Cummins 180hp engine as used by the Marcopolo buses. BMTC is going to replace only the AC Marcopolo buses with the Corona Skypak.

The Marcopolos make quite a ruckus and spew out thick black smoke.
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Old 3rd December 2011, 23:41   #26
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Originally Posted by silversteed

Wrong. BMTC has placed orders for an equal number of fully built Marcopolos, built on LPO1618 chassis, and LPO1618 chassis.

Corona Skypak bus uses the same Cummins 180hp engine as used by the Marcopolo buses. BMTC is going to replace only the AC Marcopolo buses with the Corona Skypak.

The Marcopolos make quite a ruckus and spew out thick black smoke.
I was speaking about the AC buses. In Bangalore we don't have non-ac rear engine Marcopolos.

I guess even Volvo is launching a new low floor bus for BMTC. Saw them being tested near Bommanahalli.
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Old 4th December 2011, 06:38   #27
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Originally Posted by silversteed
The Marcopolos make quite a ruckus and spew out thick black smoke.
+1 to that.
Tatas have tried to mimic the Volvo in interiors, BMTC AC Marcoplos are woefully underpowered and literally struggle to get on flyovers. But if you are anywhere near the bus ( especially behind) the thick black smoke will give you a soot shower. In fact the exhaust smoke of these Marcopolos is worse(both in quantity & quality) compared to older Tatas/ALs.

Also noticed quite a lot of Marcopolo non-AC buses in the Mysore city corporation fleet. Looks like Tata is the biggest beneficiary of the JNURM program.
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Old 4th December 2011, 08:05   #28
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Default Re: Tata Marco Polo vs Ashok Leyland Rear Engine on DTC Fleet

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Originally Posted by silversteed View Post
BMTC is going to replace only the AC Marcopolo buses with the Corona Skypak.
I don't think they are going to "replace" the AC Marcos with Corona - since the order for Corona is only 25 buses (the initial announcement was 200 buses, but now newspapers report its only 25).

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I guess even Volvo is launching a new low floor bus for BMTC. Saw them being tested near Bommanahalli.
A New Low-Floor? Can you elaborate a bit?

Volvo is reportedly developing a "lower" version of its current offerings in India - one with a lesser hp engine, and perhaps with a Low floor, instead of ULE. Is this what you saw?
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Old 4th December 2011, 09:51   #29
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Default Re: Tata Marco Polo vs Ashok Leyland Rear Engine on DTC Fleet

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A New Low-Floor? Can you elaborate a bit?

Volvo is reportedly developing a "lower" version of its current offerings in India - one with a lesser hp engine, and perhaps with a Low floor, instead of ULE. Is this what you saw?
You may wait for a month till Auto Expo to see some surprises!!
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